Hot box detector for railway rolling stock



Nov. 24, 1910 B, PORTER ETAL 3,543,929

HOT BOX DETECTOR FOR RAILWAY ROLLING STOCK Filed June 12, 1968 4 Sheets-Sheet 1 Nov. 24, 1970 PORTER ETAL 3,543,029

HOT BOX DETECTOR FOR RAILWAY ROLLING STOCK Filed June 12, 1968 4 Sheets-Sheet 2 In emuls A/mll? 2% w Mmeg Nov. 24, 1970 pom- ETAL HOT BOX DETECTOR FOR RAILWAY ROLLING STOCK Filed June 12, 1968 4 Sheets-Sheet 3 I nor- NOV. 24, 1970 PORTER ETAL 3,543,029

HOT BOX DETECTOR FOR RAILWAY ROLLING STOCK Filed June 12, 1968 '4 Sheets-Sheet 4 W 1) MM United States Patent US. Cl. 250-833 Claims ABSTRACT OF THE DISCLOSURE Apparatus is provided for the detection of overheated axle boxes on railroad locomotives and rolling stock, in which a detector unit is mounted alongside the track and looks upwards along a slant line at the leading or trailing faces of the axle boxes as they pass. The detector unit contains an infra-red sensitive indium antimonide photoconductive cell with a sensitive area in the form of a narrow rectangle elongated horizontally. The viewing beam is folded by means of two reflecting mirrors one of which is planar and of stainless steel and has various positional settings on the unit, while the other, which is protected inside a sealed window, is a powered mirror for focusing purposes. The optical system is arranged to project an additionally alongated image of the sensitive area of the cell on to each axle box While maintaining the direction of elongation horizontal. The final section of the viewing beam that impinges on the axle box face has an elevation angle from the horizontal in the range 45 to 55 and a toe-in angle in the range to 45; the toe-in angle is that angle between the vertical plane containing the beam and the vertical plane of the track rail.

This invention relates to equipment for the detection of overheated axle boxes on railroad locomotives and rolling stock.

Equipment for this purpose is known in which a detector unit is mounted alongside the track and comprises an electrical component responsive to infra red radiation and an optical system having an upwardly inclined axis for forming a spot image of that component on the sides, i.e., the leading or trailing surfaces, of the axle boxes on each passing train. It has hitherto been suggested that the detector unit should be placed outside but quite close to the rail so that the upwardly inclined viewing beam of the optical system lies in a vertical plane substantially parallel to the rail, and that the best angle of elevation of the beam is about 35. We have discovered, however, that these conditions give, in practice, results falling significantly short of the best that can be achieved. It is therefore an object of this invention to improve the performance of equipment of this type.

According to one aspect of the present invention, the infra red responsive component of the detector unit is an indium antimonide photoconductive cell, and the viewing beam of the optical system is inclined upward at an angle in the range 45 to 55 from the horizontal and lies in a vertical plane that makes an angle in the range 15 to 45 with respect to the rail.

According to another aspect of the invention, the cell is imaged on the leading or trailing faces of the passing axle boxes not as a spot but as a slot-like area elongated in a substantially horizontal direction.

The indium antimonide cell has a fast response and it is therefore possible to keep the effective frequency of the signal high, or in other words the time of sweep of each axle box low, and so achieve a short time constant which ice is of considerable benefit in reducing noise. The time of sweep is kept low by making the viewing beam as steep as possible. However, there are practical limitations to the steepness of the beam; too steep a beam will not elfectively scan certain types of axle boxes, or axle boxes in certain locations. Also, with a steep beam lying in a vertical plane substantially parallel to the rail it is found that it is difficult or impossible to scan the top center regions of the leading or trailing faces of the axle boxes; whereas the axle box faces do not become uniformly hot but it is these top center regions that are usually the hottest. Good viewing angles are: an angle of elevation from the horizontal of, say, 52 and a toe in angle, i.e., the angle between the rail and the vertical plane containing the viewing beam, of say, 30. This gives an adequate view of the various different types of axle boxes under virtually all conditions. However, it is possible to increase the angle of toe in to as much as 45 and to reduce the angle of elevation also to 45.

As already mentioned, the axle box leading or trailing face does not become uniformly hot but the hottest region is usually the center region at or near the top. It will be understood that when the upwardly inclined viewing beam has a substantial toe in angle the beam does not traverse the face of each axle box vertically but in a slant path; and variation in the height of axle boxes above the rails will cause a shift of the slant viewing path away from the top center of the box to one side or the other. Accordingly, elongation of the scanning spot in the horizontal direction greatly increases the likelihood of the hottest region of the box face being scanned and a signal read-out trace from the detector unit will give more even pulse spikes denoting the passage of the axle boxes.

One arrangement in accordance with the invention will now be described by way of example, with reference to the accompanying drawings in which:

FIG. 1 is a pictorial diagram illustrating the geometry of a system according to the invention,

FIG. 2 is a diagram showing the optical system in plan view, and

FIGS. 3 and 4 are elevations of the optical system seen, respectively, in the directions of the arrows 3 and 4 of FIG. 2.

FIG. 1 of the drawings shows the general geometry of the system. The detector unit 11 is placed alongside the track outside one rail 12 and the trailing face 10 of each passing axle box 15 is scanned by a viewing beam 13 that has an angle of elevation from the horizontal of 52 and an angle of toe in of 30 in azimuth. Due to the toe in angle the scan line of the face 10 of the axle box can be represented by the slant line 14.

FIGS. 2, 3 and 4 show the optical system of the detector unit in more detail. FIG. 2 is a true plan and FIGS. 3 and 4 are elevations seen in the directions of the arrows 3 and 4 respectively. The indium antimonide infra-red responsive photoconductive cell 16 is contained in a cell block 17 embodying optical stops 18, 19 and an optical filter 20 to limit the spectral response of the system to the required infra-red band. This cell block is offset from the vertical plane of the portion of the viewing beam that impinges on the axle boxes, as shown in FIG. 2, and the beam is folded by means of mirrors 21, 22. The mirror 21 is a stainless steel planar reflecting mirror, while the mirror 22 is a spherical concave focusing mirror.

The radiation from the axle box 15 enters the detector unit by way of a short tube (not shown) and it is reflected by the mirror 21 so that the reflected beam'makes an angle of about 60 with respect to the incident beam and lies substantially horizontal and parallel to the rail. The reflected beam passes throgh a window (not shown) to prevent dirt and moisture reaching the focusing mirror or cell, and it is then reflected a second time by the mirror 22 back on to the detector cell, the beam between the mirror 22 and the detector cell 16 lying in the horizontal plane and making an angle of about 30 with respect to the beam incident on the mirror 22.

The cell 16 has a narrow rectangular sensitive area 23 the longer dimension of which is horizontal, and the toe in of the final viewing beam impinging on the axle box elongates this rectangle still further so that the focal area 24 on the axle box face is slot-like and extends two or three inches in the horizontal direction while being about half an inch deep. The scanning beam therefore sweeps up the trailing face of the axle box in a wide slant band as indicated by the lines 25.

The distance of the focal area on the axle box from the plane mirror 21 is about 35 inches. The arrangement of the folded 'viewing beam is such that the elongated focal area is kept horizontal and does not skew. It is immaterial whether the detector cell lies on one side or the other of the vertical plane containing the section of the beam between the two unirrors. It is, however, convenient to arrange for the detector cell to lie always on the same side of that plane, irrespective of which side of the track the detector unit is placed, and simply to mount the plane mirror 21 adjustably so that it can be set to receive the beam of infrared radiation from the axle box on either side of that plane; this obviates the need to produce left-handed and right-handed units for opposite sides of the track.

We claim:

1. Apparatus for the detection of overheated axle boxes on railroad locomotives and rolling stock, wherein a detector unit is mounted alongside the track and comprises an electrical component responsive to infrared radiation and an optical system having an upwardly inclined axis for forming a spot image of that component on the leading or trailing surfaces of passing axle boxes, characterised in that the infrared responsive component is an indium antimonide photoconductive cell, and the viewing beam of the optical system is inclined upward at an elevation angle in the range 45 to 55 from the horizontal and lies in a vertical plane that makes a toe in angle in the range 15 to 45 with respect to the track rails.

2. Apparatus according to claim 1, wherein the cell is imaged on the leading or trailing face of each axle box as a slot-like area elongated in a substantially horizontal direction.

3. Apparatus according to claim 1, wherein the elevation angle is substantially 52 and the toe-in angle is substantially 30.

4. Apparatus according to claim 1, wherein the elevation angle and the toe-in angle are both substantially 45.

5. Apparatus according to claim 1, wherein the cell is housed in a cell block that is mounted at a position offset from the vertical plane of the portion of the viewing beam that impinges on the axle boxes and the beam is folded by means of optical reflecting elements so as to transfer it from said plane to a plane containing the cell.

6. Apparatus according to claim 5, wherein the optical reflecting elements include a stainless steel planar mirror.

7. Apparatus according to claim 6, wherein the optical reflecting elements include a spherical concave mirror.

8. Apparatus according to claim 7, wherein the beam enters the detector unit through a sealed window, the spherical concave mirror being inside this Window and the steel mirror outside.

9. Apparatus according to claim 7, wherein the setting of the steel mirror on the detector units can be varied to deflect the beam to one side or the other of the vertical plane containing the section of the beam between the two mirrors, for the purpose described.

10. Apparatus according to claim 2, wherein the detector cell has a narrow rectangular sensitive area the longer dimension of which is horizontal, and the optical system is arranged to maintain the image of this area on the axle box substantially horizontal while further elongating it.

References Cited UNITED STATES PATENTS 2,999,151 9/1961 Rosett 250-83.3 3,097,299 7/ 1963 Rasmusson 250-83.3 3,183,349 5/1965 Barnes et al 25083.3 3,253,140 5/1966 Sibley et al 250-8 3.3

ARCHIE R. BORCHELT, Primary Examiner M. J. FROME, Assistant Examiner 

